With the widespread use of mobile devices, there is an increasing need for the use of online storage services outside offices and homes.
In order to improve the security of content stored in an online storage, there is provided a technique of encrypting content in the online storage with a first public key and transmitting the content upon changing the encryption key from the first public key to a second public key allowing only a terminal from which a request has been received to decrypt the content.
When providing such an encryption service, it is sometimes necessary to use a special terminal to register, in a server which provides services, a new terminal which uses an online storage service. Therefore, there have been demands for a technique of registering a new terminal in a server from an arbitrary terminal which has already been registered.